Shuriken (sword hidden in the hand) are a traditional Japanese concealed weapon that were generally used by shinobi no mono (or ninja, as they are more commonly known) for throwing, and sometimes stabbing or slashing. However, the shuriken took many different shapes and designs during the time that they were used.
Hira-shuriken are constructed from thin, flat plates of metal derived from a variety of sources including hishi-gane (coins), kugi-nuki (carpentry tools), and senban (washers), and generally resemble popular conceptions of shuriken. These are sometimes called “death stars”, “throwing stars” or “ninja stars” as ninjas are consistently seen throwing this which looks like a star . They often have a hole in the center and possess a fairly thin blade sharpened only at the tip. The holes derive from their source in items that had holes - old coins, washers, and nail-removing tools. This proved convenient for the shuriken user, as well, as the weapons could be strung on a string for transport, and the hole also had aerodynamic and weighting effects that aided the flight of the blade after it was thrown. There is a wide variety of forms of hira-shuriken, also known as shaken, and they are now usually identified by the number of points the blades possess. As with bo-shuriken, the various shapes of hira-shuriken were usually representative of a particular school or region that preferred the use of such shapes, and it is therefore possible to identify the school by the type of blade used.The art of wielding the shuriken is known as shuriken-jutsu, and was mainly taught as a minor part of the martial arts curriculum of many famous schools, such as Yagyu Ryu, Katori Shinto Ryu, Itto Ryu, Kukishin Ryu, and Togakure Ryu. In the modern western world, shuriken can often be purchased online as collector’s items, but in some countries owners must possess a certificate for “knives”.
The Bo-Shuriken a throwing weapon which consisted of a straight, iron or steel spike, usually 4-sided but sometimes round or octagonal in shape. They are usually single-pointed, but there are some that are double-pointed. The length of bo-shuriken ranges from 12 to 21 cm and the average weight was from 35 to 150 grams. The bo-shuriken is thrown in a number of ways, such as overhead, underarm, sideways and rearwards, but in each case, the throw involved the blade sliding out of the hand through the fingers in a smooth, controlled flight. This is not to be confused with the kunai, which is a throwing knife.
The major forms of throw are the jiki da-ho (direct hit method), and the han-ten da-ho (turning hit method). These two forms are technically different, in that the former does not allow the blade to spin before it hits the target, while the latter requires that the blade spin before it hits the target.
Bo-shuriken were constructed from a wide variety of everyday items, and thus there are many shapes and sizes. Some derive their name from the materials they were fashioned from, such as kugi-gata (nail form), hari-gata (needle form) and tanto-gata (knife form); others are named after the object to which they appear similar, such as hoko-gata (spear form), matsuba-gata (pine-needle form) while others were simply named after the object that was thrown, such as kankyuto-gata (piercing tool form), kunai-gata (utility tool form), or teppan (plate metal) and biao (pin).